Cultures.linq

using var stream = File.OpenText(@"C:\Users\Svick\Desktop\iso-639-3.tab");
using var reader = new CsvReader(stream, new(CultureInfo.InvariantCulture) { Delimiter = "\t" });
var dict = reader.GetRecords(new { Id = "", Ref_Name = "" }).ToDictionary(x => x.Id, x => x.Ref_Name);

CultureInfo.GetCultures(CultureTypes.NeutralCultures)
    .Where(c => c.TwoLetterISOLanguageName.Length > 2 && (!dict.TryGetValue(c.TwoLetterISOLanguageName, out string isoName) || isoName != c.EnglishName))
    .Select(c => new { c.Name, c.TwoLetterISOLanguageName, c.EnglishName, IsoName = dict[c.TwoLetterISOLanguageName] })
    .Dump();